You have probably heard about melting Arctic ice and the drastic decrease in glacier size. You may have seen it yourself during a trip to a favorite spot, and mourned the loss of beautiful snow covered views. And while you may be aware that the increase in greenhouse gases is to blame, at least in large part, for our planet's warming, you may not realize that a substance called black carbon is an accomplice, affecting everything from polar bear habitat in the Arctic to glacial fed drinking water in the Himalayas. A recent peer-reviewed study found that "Most of the change in snow and ice cover -- about 90 percent -- is from aerosols. Black carbon alone contributes at least 30 percent of this sum."
Black carbon is an aerosol produced during poor combustion of carbon-based fuels (as opposed to carbon dioxide, which is produced in all circumstances), and together with organic carbon is one the major components in soot. Sources include diesel engines in various types of vehicles, furnaces, cook stoves, and forest fires, as well as some industrial processes. Some 25% to 35% of emissions occur in China and India (from combustion of wood, coal, and other fuels for household uses), whereas Europe, North America and eastern European countries emit about 13% of all black carbon, mostly from contained combustion.
Black carbon absorbs visible light and transfers the energy to the atmosphere, warming it. While carbon dioxide can stay in the atmosphere for 100 years, black carbon has a short atmospheric lifetime, making its effects more concentrated near the areas where it is emitted, especially in terms of atmospheric warming and health issues due to inhalation. It settles quickly from the atmosphere, and when it lands on snow and ice, the darkened snow and ice absorb more heat and melt more quickly. Because most emissions occur above 40⁰N, where they are likely to be transported to the Arctic (see Princeton University Report), black carbon has been linked to the melting of Arctic ice and Himalayan glaciers.
Various authors and policy makers advocate targeting black carbon as a more effective warming reduction tool in the near term, without forgetting that, in the long run, reducing greenhouse gases is the only way to reduce global warming. The arguments for black carbon reduction are especially cogent because technologies to reduce black carbon emissions already exist, such as retrofitting diesel vehicles with filters or switching from diesel to natural gas, and replacing inefficient cook stoves with cleaner burning ones. Recently, Conservation Magazine published an article on the efforts to create a cleaner-burning stove that would be affordable to the communities in Africa that depend on them. The effort involved, the details entailed, and the determination of a few engineers are mind-blowing. To quote that article:
The average cooking fire produces about as much carbon dioxide as a car, and a great deal more soot, or black carbon -- a substance 700 times as warming. [...] Given that cooking fires each release 1,000 to 2,000 grams of soot in a year and that 3 billion people rely on the fires, cleaning up those emissions may be the fastest, cheapest way to cool the planet.
More importantly, reducing black carbon emissions will also improve the quality of life and health of the communities most impacted by it, especially in developing countries.
Black carbon had not been formally addressed as a warming agent, or a possible target for decreasing global warming, in the United Nations Framework Convention on Climate Change (UNFCCC). However, on June 14 the United Nations released a report which states that cutting black carbon and methane emissions would slow the rate of warming until about 2040. As a result, black carbon will be addressed by the UNFCCC for the first time at the COP 17 in Durban this coming November/December.